To test the theory, researchers took a group of smokers in the U.S. and showed them a number of pictures. Some of the pictures included no smoking signs in the background and some had the signs edited out.

The participants then took a "joystick test", which looks at their reactions to the images. Participants move the joystick away from the body to avoid the action and draw the joystick toward the body to bring the stimulus closer. Smokers were more likely to want to light up after seeing the signs compared to those who didn't see the signs.

"It's a significant effect which we think would have real life implications," says Earp in a Daily Mail article. Earp, a graduate student at Oxford, presented the findings at the British Psychological Society's annual meeting last week.

"No Smoking" signs are meant to discourage an activity but what happens is you get a kick back so that the very item that's supposed to be prohibited becomes desirable."

Similar to the U.K., "No Smoking" signs are everywhere in Canada. Smoking in Canada is banned in all indoor public spaces and workplaces including restaurants and bars. Some provinces even prohibit smoking in private vehicles if a child under the age of 16 is riding in it.

About half of the United States has banned smoking in bars, restaurants and workplaces. These bans are expected to cover the whole country by 2020.

His research suggests people may obey and respect public health messages if they are framed with positive wording. This is similar to what many lifeguards are taught. Instead of telling someone to not run on the deck, they are encouraged to tell people to please walk on the deck.

Earp tells the Daily Mail, "My hunch is that having all this 'don't do this' information out there may have ironic consequences."

So should "No Smoking" signs be changed to say "Breathe clean air only" or "Enjoy this clean air environment?"